1. Field of the Invention
The present invention relates to a display apparatus and a method of controlling the same, and more particularly, to a display apparatus and a method of controlling the same, which can prevent error data from being stored in an extended display identification data (EDID) storage.
2. Description of the Related Art
Recently, a display apparatus with Plug and Play functionality has been greatly universalized.
The display apparatus with the Plug and Play functionality can exchange information with a computer while a conventional display apparatus only receives a signal from the computer. When the display apparatus is just plugged into the computer and turned on, such display apparatus with the Plug and Play functionality allows the computer to automatically optimize user environments relating to the display apparatus and also allows a user to directly use the display apparatus.
To provide the Plug and Play functionality to the display apparatus, the display apparatus must previously store extended display identification data (EDID), such as a manufacturer identification (ID), a model name ID, a display power management signaling function supportability, etc., and a protocol for data communication between the display apparatus and the computer must be previously set.
Therefore, a display data channel (DDC) standard was created by the video electronic standard association (VESA) to define a standard for the data communication of the display apparatus having the Plug and Play functionality.
The DDC standard defines data communication channels between the display apparatus and the computer as a protocol for transmitting display data stored in the display apparatus to the computer or changing the display data through a keyboard, a mouse, etc.
The DDC standard includes various DDC levels such as DDC1, DDC2B, etc.
In the DDC1, the display data is transmitted from the display apparatus to the computer one bit by one bit in correspondence to a vertical synchronous signal transmitted from the computer. As long as the vertical synchronous signal is inputted to the display apparatus, the display apparatus continuously and circularly transmits the EDID having a data size of 128-bytes to the computer.
In the DDC2B, when the computer asks for the EDID of the display apparatus through a serial data line (SDA) and a serial clock line (SCL), the display apparatus transmits the EDID to the computer through the SDA.
FIG. 1 is a block diagram of an EDID storage and peripherals in a conventional display apparatus.
As shown in FIG. 1, in a conventional display apparatus, an EDID storage 110 is operated by at least one of a display power and a computer power. Further, the EDID storage 110 includes a write-protect (WP) port being grounded.
Here, when the WP port is in a high state, it is allowed to only read data from the EDID storage 110. In contrast, when the WP port is in a low state, it is allowed to read data from and write data to the EDID storage 110.
However, the conventional display apparatus is allowed to write data to the EDID storage 110 so long as the computer power is supplied to the EDID storage 110 regardless of the display power. Therefore, error data may be unexpectedly written to the EDID storage 110 because of an electrostatic discharge (ESD) or application malfunction while the computer is being used.
Further, in a case when the computer is turned off while accessing the EDID storage 110 to read the EDID, the data communication is interrupted and therefore the EDID storage 110 cannot receive a clock signal from the computer through the SCL, so that the EDID storage 110 becomes abnormal.
Further, in a case when the computer is turned on while the EDID storage 110 is operated by the display power, the EDID storage 110 may be supplied with an unstable power due to the computer power. In this case, if the computer accesses the EDID storage 110, the data communication is inaccurately performed.